The invention relates to a remote controlled aircraft or drone in particular for surveillance or inspection, for example of works of art, suspended cables, high voltage power lines, nuclear installations, etc.
Such an aircraft is generally equipped with observation and detection means, in particular a camera for producing images of overflown zones, allowing both visual inspection of the zones and allowing the aircraft to be piloted by sight, and a propeller or rotor with a vertical axis allowing vertical takeoff and hovering.
Mounting the propeller in a cylindrical fairing has already been proposed to slightly reduce the dimensions of the propeller for the same thrust and to reduce the risks of the rotating propeller impinging on surrounding objects or personnel.
The invention aims to substantially improve that type of aircraft to enable it to be used in complete safety and to substantially improve its performance and versatility in service.
The invention also aims to provide such an aircraft that can take off and land substantially vertically, move in forward flight and hover.
To this end, the invention provides a remote controlled aircraft provided with observation and/or detection means, a propeller with a vertical axis rotating inside a substantially cylindrical fairing and an engine powering the propeller, characterized in that the centre of gravity of the aircraft is located below its geometrical centre and in that the assembly comprising the detection and/or observation means, the engine and the propeller is surrounded by a substantially spherical open-worked outer cage that is integral with the fairing.
By dint of these characteristics, the aircraft of the invention can take up a stable position on the ground in which the axis of the propeller is substantially vertical. It can take off vertically, land on the ground and automatically adopt its stable position, and take off again vertically. Further, in the event of a shock to the aircraft against an obstacle, the outer cage protects the aircraft from damage and also protects the obstacle struck by the aircraft.
Advantageously, the outer cage is formed from at least one material that is light and shock resistant.
In one embodiment of the invention, at least a portion of the cage is formed as a single piece with the fairing and is preferably formed from a closed cell plastics material such as a polyethylene foam.
In a variation, said cage is at least partially metallic and comprises a grill or screen fixed or locked into the fairing.
In a further feature of the invention, the aircraft comprises an axial fuselage the aft portion of which contains the engine and the observation and/or detection means, and redressing vanes extending aft of the propeller between the fairing and the axial fuselage to prevent the aircraft from rotating about the axis of the propeller. In a particularly simple embodiment of the invention, said redressing vanes are fixed. In a more sophisticated and expensive embodiment, said redressing vanes can be orientated about an axis perpendicular to the axis of the propeller and are controlled by servo-motors.
In a further characteristic of the invention, said aircraft also comprises control surfaces formed by flaps or ailerons which extend in the aft portion of the aircraft between the fuselage and said cage and which can be orientated about axes perpendicular to the axis of the propeller to direct the aircraft by rotation about its pitch, yaw and/or roll axes.
A control circuit comprises a microprocessor and optionally at least one gyroscope that can determine the appropriate values for the engine speed and for the position of the redressing vanes and/or control surfaces as a function of the commands given by an operator (for example climb or descend, move forward, turn to left or to the right, move backwards).
In a first embodiment, the aircraft is equipped with an electric motor and storage batteries, the latter being located inside the axial fuselage or carried by the fairing.
In a further embodiment, the aircraft is equipped with a heat engine and a fuel tank, the latter being located inside the axial fuselage or carried by the fairing.
The invention also envisages means for dynamic stabilisation of the aircraft in transitional motion, comprising a mobile mass-balance weight mounted as an inverted pendulum on the axis of the propeller forward thereof. Elastically deformable return means and means for dampening the displacement are associated with said mobile weight.
Displacement of said mobile mass-balance weight is phase opposed with any angular drift of the aircraft compared with a desired trajectory and can limit it and slow it sufficiently to correct it manually or automatically.
The stabilisation means can be passive or active. In the latter case, they are associated with servo-motors which can be controlled either by an operator or automatically, for example using an inertial onboard navigation platform or a remote image treatment system, which can obtain references, in particular vertical references, from images transmitted by the observation means of the aircraft.
The aircraft of the invention can have a wide range of dimensions depending on the tasks it is intended to fulfil. Its design enables it to be produced with simple means that are commercially available at a relatively low cost.